You're right, shipping speed likely also factors into it in addition to cost (that's why I also mentioned the shipping speed). If Amazon can't deliver within it

You're right, shipping speed likely also factors into it in addition to cost (that's why I also mentioned the shipping speed). If Amazon can't deliver within its 2-day Prime guarantee it is less likely to promote the offer. Of course, without access to Amazon's systems I can't say for sure why any individual listing is or is not promoted. I'm just making an educated guess based on what the FTC put in its complaint.